Switching to 75W-140 Oil for towing JKs

[HeliNomad]

Guys,

I have a 2014 JK Rubicon Unlimited that frequently tows a heavy Chaser trailer. Should I switch the rear diff to 75W-140 oil as the owners manual states. I use all Amsoil signature fluids but haven't switched anything yet as the truck only has 1,900 miles on it. Whats the suggested route? Cost is not a factor here.

 

[JIMBO]

:sombrero: I've been running Valvoline 75w-140 syn, in both my diffs for over two years-

I also tow a tentrax that avg/1100 lbs, but I use the Valvo/75w-140 anyway, because it's a cut above the 75w-90 syn !

My rear diff usually runs about 75/85°F at freeway speeds while towing, course I run 5.38 gears too--Higher ring/pinion rpm, but less gear load stress !

:costumed-smiley-007:wings: JIMBO

 

[HeliNomad]

So should I run it in the front also? Manual only calls for rear.

 

[JIMBO]

:sombrero: Well, the manual calls for it's use when under load-(off-road/tow/police) and It's a superior diff fluid-

I useit in the front because it's a better gear lubricant and I buy it by the case, so it's about $13.50 a quart !

So should I run it in the front also? Manual only calls for rear.

No reason to useit in the front except your own satisfaction !

Good luck

:costumed-smiley-007:wings: JIMBO

 

[Verbal]

I switched to the 75w-140 syn before towing a 5500 lb, 5x10 enclosed haulmark trailer 2300 miles. So far so good. Granted I have a KJ, not a JK... lol

 

[HeliNomad]

I switched to the 75w-140 syn before towing a 5500 lb, 5x10 enclosed haulmark trailer 2300 miles. So far so good. Granted I have a KJ, not a JK... lol

Did you put it in the front also?

 

[brianjwilson]

I run 75/140 front and rear too. No particular reason for running it up front, I just bought four quarts that were all the same. Since the front diff is under no load there is no reason to run it. Lower gears might cause a little more heat I suppose but otherwise...?

 

[HeliNomad]

Any notice of a lower MPG after switching? Or a change in the operation of the stock lockers?

 

[JIMBO]

:sombrero: Yeah, when I put my 75w-140 in both diffs, I immediately saw a 20% increase in gas mileage---

Any notice of a lower MPG after switching? Or a change in the operation of the stock lockers?

Oh, incidentally that was the same time in regeared to 5.38 Yukon gears--went from 15 mpg to over 18 mpg-

I doubt if you'd be able to show a factual increase in JUST changing to the 75w-140 though-

I have shown a factual cooler rear differential, after running at 70 mph for 1 hour--the rear diff avg temp was 80° F so, even though the ring pinion were running higher rpm (5.38) the 75w-140 syn kept them cooler-

Can'tbeatit

:costumed-smiley-007:wings: JIMBO

 

[Verbal]

I didn't notice any difference in MPG's but I'm also diesel powered :wings:

 

[Verbal]

I run 75/140 front and rear too. No particular reason for running it up front, I just bought four quarts that were all the same. Since the front diff is under no load there is no reason to run it. Lower gears might cause a little more heat I suppose but otherwise...?

Most of our voyage was snow-packed so we were towing and running 4wd... figured better safe than sorry.

 

[HeliNomad]

Can I fill both diffs with 4 quarts total?

 

[SiliconTi]

Can I fill both diffs with 4 quarts total?

Easily. Front holds 1QT, rear 1.5 or so, IIRC.

I run Lucas full synthetic (front and rear) and had a front pinion bearing fail (JKUR). I'll probably try Royal Purple next time.

 

[irish1371]

if your already running amsoil I doubt your going to see a difference by changing weights. You may want to look into a different diff cover. The heavy duty ones like solid and riddler would not dissipate heat as well as an arb or any that are "finned".

I have used amsoil for years with great results I would love to see a heat comparison between regular amsoil and a 90-140 synth and then maybe a stock dino filled diff. Would be very interesting

 

[HeliNomad]

Should I change the transmission and transfer case with the Amsoil signature equivalent also? I mean I'm doing everything else on the truck with the diffs now. Thanks for the advise.